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When I was a kid, I remember people talking about putting on suntan lotion to help them absorb the sun’s raise. Those days are over. Too much sun can be terrible for you. Besides to the fact that it’s significantly increases the risk of skin cancer, the sun will age your skin and make you look older too. Who wants that? Today, we use sunscreen to protect us from the sun, but most of us are doing it wrong. How so? Sunscreen is the topic of this week’s Healthcare Triage.

Right off the bat, before I say anything else, I want you to hear that you absolutely should use sunscreen. Exposure to the sun’s ultraviolet rays both UVA and UVB causes damage to the skin which can lead to skin cancer. UVB rays are the ones that cause most sunburn, but UVA rays which penetrate deeper into the skin cause the skin to wrinkle and sag and get leathery and all of those other things we’d like to avoid, so use sunscreen.

Sunscreens with an SPF of 15 or higher really do protect your skin against the sun. I know there was a recent study showing that women who didn’t get any sun have an overall higher mortality than women who do. I’ve seen all the articles on Facebook, so let’s spend a minute talking about that. To the research.

Researchers followed almost 30,000 women in the Melanoma in Southern Sweden or MISS cohort. Over 20 years, 2545 of them died. Women who avoided the sun completely were twice as likely to die as women who sunbath. Scary, right? First of all, the absolute rate difference was 3% to 1.5%. Yes, the headline said doubled, but that’s a relative risk and we all know the difference, right?

Next, even this study found that sun exposure was significantly linked to melanoma risk. That’s still true. Third, observational studies like this are going to be confounded, meaning there could be something they’re not measuring that’s causing the results. For instance, is it that hard to imagine that active people are more likely to be exposed to sun than totally sedentary people? Sedentary people can have a higher risk of death.

A lot of the articles you all keep sending me on Facebook seem to be obsessed with the idea that this is somehow caused by vitamin D. This study had nothing to do with vitamin D. There’s no measurement of vitamin D. No way to know if anyone is vitamin D deficient. No vitamin D variables at all. None. Finally, this is not a randomized control trial. There’s no causality here. There are however randomized controlled trials showing that sunscreen prevents melanoma and skin aging.

Sunscreen works. Use it. It comes in two types. Organic and inorganic. Organic doesn’t mean natural like it does with food, it refers to the chemical definition. Organic compounds are carbon-based and that’s true of sunscreens as well. Organic sunscreens are absorbed into the skin. There, they absorb the UV rays of the sun and then let the energy dissipate in more safe ways. Inorganic sunscreens in the other hand are physical blockers. They sit on top of the skin and reflect UV rays away from the body. The organic kind are much more common, but both are fine.

The first problem is that we don’t use nearly enough. You should be using it at least one ounce of the equivalent to one shot glass bowl. This is the official recommendation. You should use 2mg of sunscreen per centimeter square to your body which equates to two finger lengths of product applied to all 11 areas of the body. You also need to keep reapplying the stuff to make it work. Recommendations say that you should put sunscreen on 30 minutes before you go out in the sun to let the ingredients bind to the skin. Then ideally, you should put another application on 20 minutes later.

Studies show that this early reapplication is even better than waiting than two hours which is also a usual recommendation. Then you only need to reapply the sunscreen again if you go swimming, if you towel off, if you vigorously sweat. Basically if you’re outside in the sun. I’d like to point out that it’s somewhat ridiculous to expect people to follow recommendations like this. They just won’t do it. If you stay at the beach all day, that would mean that you should use up most of your bottle of sunscreen. Who does that?

One could argue, and I’m happy to raise this argument, that the amount of protection promised on the bottle of sunscreen should be based on the actual amounts that people usually apply to their skin. Not the amount people used in the lab under unrealistic conditions. Using average application amounts, the protection from sunscreen is probably half or less than half of what’s listed on the bottle.

Moving on, if you believe what you see on TV, you might think that you need SPF one gazillion to be protected. Is that so? No. First of all, the difference between sunscreens with SPF 30, 45, 50 and 60 is 1.6% or less. Sunscreen with SPF 15 blocks approximately 94% of all incoming UV rays. Sunscreen with SPF 30 blocks 96% of the UV rays. Sunscreen with SPF 40 blocks 97% of the rays.

Higher SPF sunscreen does block more UV rays and they’re better in that sense, but they’re really not that much better. It’s not clear how much better they can get if you go above 50. Not that that stop companies from selling sunscreen at SPF a hundred and more. Additionally, I know plenty of people who think that if they use SPF 60 instead of SPF 30, they only need half as much. That’s just not true at all. You’ve gained a few percentage points of protection at best than only if you’re applying in huge amounts over and over and over again.

Ironically, besides being more expensive, the higher SPF formulation seem to come in smaller and smaller bottles making using the correct amounts almost impossible. You’d probably be much better off buying the SPF 15 or 30 by the gallon and then applying it all over again and again. That’s how you protect yourself from the sun. Stop worrying about the SPF and start worrying about how you put it on. That’s how you do it right.

By the way, this episode of Healthcare Triage is supported by Audible.com, a leading provider of premium digital spoken audio information and entertainment on the internet. Audible.com allows its users to choose the audio versions of their favorite books with a library of over 150,000 titles. We recommend the Sun Also Rises by Ernest Hemingway because it involves the sun. You can download a free audio version of the Sun Also Rises or another of your choice at Audible.com/triage.